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APR-DRG

Last updated: 05-21-2025
ColumnData TypeDescriptionTerminology
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What are APR-DRGs?​

APR-DRG stands for All Patient Refined Diagnosis Related Groups. It is a patient classification system that categorizes hospital stays into groups based on clinical similarity and resource usage, incorporating both severity of illness (SOI) and risk of mortality (ROM).

APR-DRGs are designed to better reflect the complexity of care across all patient populations, including neonates, pediatrics, and adults.

Who Created APR-DRG?​

APR-DRGs were developed by *3M Clinical and Economic Research Department in collaboration with the Children's Hospital Association and several physician groups. The system builds upon the earlier work on Refined DRGs by Yale University.

APR-DRG assignment is based on diagnosis and procedure codes submitted on inpatient claims, using the ICD-10-CM (diagnosis) and ICD-10-PCS (procedure) classification systems. The grouping logic maps combinations of codes to a base DRG, then assigns levels for severity of illness and risk of mortality.

How are APR-DRG Codes different from MS-DRG Codes?​

While MS-DRGs (Medicare Severity DRGs) are used primarily by Medicare for payment of adult inpatient hospital stays, APR-DRGs are designed to:

  • Capture a broader population, including pediatrics and obstetrics.
  • Include four severity of illness (SOI) and four risk of mortality (ROM) subclasses per base DRG.
  • Provide greater granularity for comparing resource utilization and outcomes across hospitals.
  • Be used more often in state Medicaid programs and commercial payers.

MS-DRGs, by contrast, use fewer subclasses and are more focused on Medicare beneficiaries and payment alignment.

Who Maintains APR-DRG Codes?​

APR-DRGs are maintained by Solventum, a spin-off of 3M Health Care, a private company. Unlike MS-DRGs (which are publicly available through CMS), the use of APR-DRGs typically requires a commercial license.

Organizations that wish to use the official grouping logic or software must obtain a license from 3M.

On what kind of claims are APR-DRG Codes found?​

APR-DRG codes are found on inpatient facility claims. They are most commonly used in:

  • State Medicaid programs
  • Commercial insurers
  • Children’s hospitals and academic medical centers

They are not typically found on Medicare fee-for-service claims.

Like MS-DRGs, APR-DRGs serve as a proxy for resource intensity and hospital cost. The assigned APR-DRG, in combination with its severity level, can drive:

  • Reimbursement rates
  • Cost benchmarking
  • Performance measurement

Some payers may assign weights to each APR-DRG and SOI combination to calculate expected payment or cost.

Code Structure​

An APR-DRG code has the following structure:

  • Three-digit base DRG (e.g., 139 – "Other Pneumonia")
  • Two single-digit modifiers:
    • Severity of Illness (SOI): 1 (minor) to 4 (extreme)
    • Risk of Mortality (ROM): 1 (minor) to 4 (extreme)

A complete grouping might be expressed as:
139-3-2 = DRG 139, SOI level 3, ROM level 2

Some systems may concatenate these into a single string (e.g., 13932).

Notes for Analysts​

  • APR-DRGs are often not present in publicly available claims data, especially Medicare FFS. Verify availability before use.
  • A single DRG (e.g., 139) may be split into 16 possible combinations (4 SOI × 4 ROM).
  • Severity levels are relative and based on clinical coding, not lab values or vitals.
  • Inpatient claims without APR-DRGs may occur if the grouper was not applied or if licensing is restricted.

Key Use Cases for APR-DRG Codes​

  • State Medicaid rate setting
  • Children’s hospital comparisons
  • Quality and outcome benchmarking
  • Case-mix adjustment for pediatric and obstetric populations
  • Population health analytics for commercial insurers

Tuva Seed File Update Process​

Note: This is the maintenance process used by Tuva to maintain the current codeset in the Tuva package. Tuva users do not need to complete this step unless they are leveraging a different version of codes or are no longer updating to the current version of the project, but need an updated terminology set.

  1. Navigate to the Solventum APR DRG page
  2. Find the description files worded 'Solventum APR DRG descriptions'
  3. Open the latest description file, named 'APR DRG <latestversion> descriptions'
  4. Copy the code block from the file and paste it into a text editor.
  5. Format the codes as a CSV file and save
    • You can paste it into Google Sheets or Excel
    • Use the pipe symbol (|) as the custom delimiter
    • Save/export the sheet as a .csv file
  6. Import the CSV file into your data warehouse
    • Ensure that empty fields are imported as null, not blank strings ('')
  7. Transform the uploaded data to another table to match the Tuva Terminology standard:
    • DRG → apr_drg_code
    • Type → medical_surgical
    • MDC → mdc_code
    • Long Description → apr_drg_description
  8. Unload the table from the data warehouse to a CSV file in S3 (credentials with write permissions to the S3 bucket are required)
-- example code for Snowflake
copy into s3://tuva-public-resources/terminology/apr_drg.csv
from [table_created_in_step_7]
file_format = (type = csv field_optionally_enclosed_by = '"')
storage_integration = [integration_with_s3_write_permissions]
overwrite = true;
  1. Create a branch in docs. Update the last_updated column in the table above with the current date
  2. Submit a pull request

The below steps are only required if the headers of the file need to be changed. The Tuva Project does not store the contents of the terminology file in GitHub.

  1. Create a branch in The Tuva Project
  2. Copy and paste the updated header into the APR-DRG file
  3. Submit a pull request